Sedimentary Organic Matter: Origin, Productivity, Preservation, and Role in Source Rock Development

Accurate source rock characterizations via geochemical and optical methods require advanced knowledge of the processes of their formation and the factors that control their development. The current chapter starts by addressing the fundamentals of sedimentary organic matter’s origin and chemical compositions and how they interact with the atmosphere, lithosphere, and hydrosphere through comprehensive elucidations of the biogeochemical cycles of carbon, nitrogen, sulfur, and phosphorus. Then, it discusses the deposition and transportation of organic matter in different habitats and the physical and chemical factors that affect its preservations. The third part of the chapter provides insights into the kerogen formation pathways, classifications, and alteration processes. Finally, the chapter introduces the common terrestrial and marine source rock depositional environments and the processes that control the organic productivity and source rock development richness and quality. The knowledge in this chapter represents a reliable base for accurate source rocks and petroleum data interpretations. Furthermore, it can assist in explaining the changes in organofacies and thermal maturity, identifying sweet spots in unconventional resources, types of generated hydrocarbons (sweet versus sour oils), and maturing basin modeling calibrations.